Definition of Phenomenon, Babinski

Babinski phenomenon: A neurologic reflex that constitutes
an important medical examination based upon what the big toe does
when the sole of the foot is stroked. If the big toe goes up, that
may mean trouble.

The Babinski reflex is obtained by stimulating the external
portion (the outside) of the sole. The examiner begins the
stimulation back at the heel and goes forward to the base of the
toes. There are diverse ways to elicit the Babinski response. A
useful way that requires no special equipment is with firm pressure
from the examiner's thumb. Just stroke the sole firmly with the thumb
from back to front along the outside edge.

Too vigorous stimulation may cause withdrawal of the foot or toe,
which can be mistaken as a Babinski response.

Most newborn babies are not neurologically mature so they normally
give a Babinski response. Upon stimulation of the sole, they extend
the great toe. Many young infants do this, too, and it is perfectly
normal. However, in time during infancy the Babinski response
vanishes and, under normal circumstances, should never return.

A Babinski response in an older child or adult is abnormal. It is
a sign of a problem in the central nervous system (CNS), most likely
in a part of the CNS called the pyramidal tract.

Asymmetry of the Babinski response -- when it is present on one
side but not the other -- is abnormal. It is a sign not merely of
trouble but helps to lateralize that trouble (tell which side of the
CNS is involved).

The Babinski reflex is known by a number of other names: the
plantar response (because the sole is the plantar surface of the
foot), the toe or big toe sign or phenomenon, and the Babinski sign.
(It is wrong to say that the Babinski sign is positive or negative;
it is present or absent).

Babinski, despite the Slavic sound of the name, was French: Joseph
Francois Felix Babinski (1857-1932). His name will not be soon
forgotten in medicine, thanks to the Babinski phenomenon.